Storage stability of fluid bed dried solid state fermented (SSF) lactic cultures inmilk

Abstract

The present investigation was intended to study theeffect of storage at ambient temperature on the fluid beddried powder of Solid State Fermented (SSF) lactic cultures such as dahi, yoghurt and probiotic cultures and also made an attempt to check the performance in milk. The SSF cultures were prepared from various dhals and screened for the survival of bacterial aerobic spore, the raw black gram dhal showed lowest spore count of 1.52 log10cfu/g. Combination of hot air oven exposure of black gram dhal at 1000C/1 h and sterilization at 1210C/30 min completely destroyed the spores. On fermentation the maximum viable counts of dahi (8.41log10cfu/g), yoghurt (8.98log10cfu/g) andprobiotic (9.47log10cfu/g) cultures were obtainedon black gram dhal containing 1:0.8 ratio of moisture was supplemented with 1% level of skim milk powder, ash gourd, carrot and tomato juices as they provided growth promoting agents. The fermented SSF cultures were subjected for fluid bed drying for 1.5 h at ambient temperature (250C).The SSF culture viability upon fluid drying decreased from 8.65 to 8.33, 9.01 to 8.85 and 9.65 to 9.34log10cfu/g in case of dahi, yoghurt and probiotic cultures, with the moisture content of 9.4%. When these dried powders of SSF cultures of dahi, yoghurt and probiotic cultures were inoculated at 1,0.5 and 3% to heated milk, the cultures took 5:00, 3:30 h and 9:30 h to set the heat treated milk with acidity of 0.68, 0.71 and 0.59% lactic acid respectively. The dried SSF lactic cultures possessed viability of 6 log10cfu/g till 24th days of storage at ambient temperature (28±10C) and these cultures showed absence for the contaminants like coliforms, aerobic spores and yeast and molds. With respect to performance, the curdling time increased with theincreased storage days at ambient temperatures due to the reduction in viable lactic counts.